import java.awt.Graphics;
import javax.swing.JPanel;

public class Circulo extends JPanel
{
    public void paintComponent( Graphics g)
    {
        super.paintComponent(g);
        
        int centrox=getWidth()/2-10;
        int centroy= getHeight()/2-10;
        
        for(int i=1;i<=12;i++)
        {
        
            g.drawOval(centrox,centroy,i* 20,i*20);
            centrox-=10;
            centroy-=10;
        }
    }
}